Method for producing unhaired hides with the aid of mold tryptases



Patented @ct. Ii, 1938 METHOD FOR PRODUCING HIDES WITH THE AID OF MOLD TRY]?- TASES Otto Riihm, Darmstadt, Germany No Drawing. Application'March 25, 1936, Serial No. 70,890. In Germany April 2, 1935 6 Claims. .(Cl. 195-6) The invention relates to preparing hides or skins for tanning, and more particularly to subjecting such hides or skins for depilating and/or bating purposes to neutral or weakly acid solutions containing mold tryptase, particularly those produced by the Aspergillus varieties, in the presence of sodium bisulphite.

It is known to bate and dehair skins and hides with the aid of pancreatic enzymes, particularly the tryptases.

In the bating process, ammonium salts are generally used along with the enzymes; due to the action of the lime content of the hides, these produce ammonia.

16 In the depilatory process, sodium bicarbonate is largely usedwhich, on reaction with the caustic soda content of the hide, is transformed into sodium carbonate.

Hence, in one case ammoniacal and in the other case soda-containing hides are obtained. This condition of the hides has the drawback that when these hides encounter calcium bicarbonate or calcium sulphate or water containing both, insoluble calcium carbonate is formed which settles out mainly on the grain of the hide and subsequently deleteriously affects the dyeing capacity of the leather. A further drawback resides in the fact that the so-called basic hairs are sometimes difficult to remove.

30 Various attempts have been made to .replace the pancreatic tryptase by mold tryptases and to operate in alkaline, acid, or even neutral solutions. But in using mold tryptases difficulty has always been experienced in removing the base 35 and basic hairs.

It has been found that all of the aforesaid drawbacks may be obviated when mold tryptases, particularly those produced by the Aspergillus varieties, of which Aspergz'llus flavus is an example, are used in neutral to weakly acid solutions together with sodium bisulphite. By this procedure clean hides completely free from basic hairs have been obtained to an extent not entirely achievable hitherto. This procedure also requires that the use of alkali be reduced to about half It has further been found that the action of the solution used in accordance with the invention may be further improved by the addition of ammonium salts, e. g. ammonium sulphate.

Examples 1. 100 kgs. of calf hides, softened as. usual, are

treated with 500 liters water, 1.8 kgs. caustic soda,

the hides are placed the dehairing bath with 500 liters water of C., 3 kgs. sodium bisulphite,

-5 kgs. common salt, and 1 kg. mold tryptase.

After one day the hides are obtained in a depilated condition, free from basic hairs. The hides 5 :nay then be worked up without subsequent bat- 2. 100 kgs. calf hides, softened as usual, are treated with 500 liters water, 1.8 kgs. caustic soda, and 1.2 kgs. sodium sulphate. After two to three 10 days the hides are placed in the depilating bath with 500 liters water at 25 C., 2.3 kgs. sodium bisulphite, 1.5 kgs. ammonium sulphate and 1 kg. mold tryptase. After one day they are depilated free from basic hair. The hides may then be is worked up as usual without subsequent bating.

3. Ordinary lamb hides treated with limearsenic are (after the wool is removed) washed for two hours with soft water and then each 100 kg. weight of hide is bated with 300 liters water 20 at 25-30 0., 2 kgs. sodium bisulphite. 1 kg. ammonium sulphate and .35 kg. mold tryptase. The

bating may be carried on over night. The next morning the hides are worked up as usual, that is,de-fleshed, smoothed, washed and finished. 5

I claim:

1. A method of preparing hides or skins for tanning, which comprises pre-treating the hides with an alkaline reagent and then subjectin the pre-treated hides or'skins for depilating and bating purposes to a neutral to weakly acid solution containing a mold tryptase together with sodium bisulphite.

2. A method of preparing hides or skins for tanning, which comprises pre-treating the hides with an alkaline reagent and then subjecting the pre-treated hides or skins for depilating and bating purposes to a neutral to weakly acid solution containing a mold tryptase together with sodium bisulphite and an ammonium salt. 40

3. A method of preparing hides or skins for tanning, which comprises pre-treating the hides with an alkaline reagent and then subjectin the pre-treated hides or skins for depilating and bating purposes to a neutral to weakly acid sclu- 5 tion containinga mold try tase together with sodium bisulphite' and amn onium sulphate.

4. A method of preparin; hides or skins for tanning, which comprises pie-treating the hides with an alkaline reagent and then subjecting the pre-treated hides or skins for depilating and bating purposes to a neutral to weakly acid solution containing a mold tryptase together with sodium bisulphite, the tryptase being derived from Aspergillus varieties. B6

5. A method of preparing hides or skins for,

tanning, which comprises pre-treating the hides with an alkaline reagent and then subjecting the pre-treated hides or skins for depilating and bating purposes to a neutral to weakly acid solution containing a mold tryptase together with sodium bisulphite, the tryptase being derived from Asper gillus flavus. v

6. In a process for preparing hides or skins for tanning which includes the steps of pre-treatin'g the hides with an alkaline reagent and then subjecting the pre-treated' hides Ior'depilating or hating to a solution containing a mold tryptase; the improvement which consists in carrying out the depilatin and hating treatment with the tryptase in a neutral to weakly acid solution in the presence of sodium bisulphite.

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